Microstimulators are known in the art. For example, in U.S. Pat. No. 5,312,439, incorporated herein by reference, entitled “Implantable Device Having an Electrolytic Storage Electrode,” an implantable micro-stimulation device for tissue stimulation is described. The described microstimulator shown in the '439 patent relates to an implantable device using one or more exposed, electrolytic electrodes to store electrical energy received by the implanted device, for the purpose of providing electrical energy to at least a portion of the internal electrical circuitry of the implantable device. It uses an electrolytic capacitor electrode to store electrical energy in the electrode when exposed to body fluids.
Another microstimulator known in the art is described in U.S. Pat. No. 5,193,539, “Implantable Microstimulator”, which patent is also incorporated herein by reference. The '539 patent describes a microstimulator in which power and information for operating the microstimulator is received through a modulated, alternating magnetic field in which a coil is adapted to function as the secondary winding of a transformer. The induction coil receives energy from outside the body and a capacitor is used to store electrical energy which is released to the microstimulator's exposed electrodes under the control of electronic control circuitry.
In U.S. Pat. No. 5,193,540, which patent is likewise incorporated herein by reference, a structure and method of manufacture of an implantable microstimulator is disclosed. The microstimulator has a structure which is manufactured to be substantially encapsulated within a hermetically-sealed housing inert to body fluids, and of a size and shape capable of implantation in a living body, with appropriate surgical tools. Within the microstimulator, an induction coil receives energy from outside the body requiring an external power supply. Another method of manufacturing a microstimulator is found in U.S. Pat. No. 5,405,367, which patent is also incorporated herein by reference and which patent is a continuation of the '540 patent.
In yet another example, U.S. Pat. No. 6,185,452, which patent is also incorporated herein by reference, describes a device configured for implanting beneath a patient's skin for the purpose of nerve or muscle stimulation and/or parameter monitoring and/or data communication. Such a device contains a power source for powering the internal electronic circuitry. Such power supply is a battery that may be externally charged each day. Similar battery specifications are found in U.S. Pat. No. 6,315,721, which patent is incorporated herein by reference.
Other microstimulator systems prevent and/or treat various disorders associated with prolonged inactivity, confinement or immobilization of one or more muscles. Such microstimulators are taught, e.g., in U.S. Pat. Nos. 6,061,596 (Method for Conditioning Pelvis Musculature Using an Implanted Microstimulator); 6,051,017 (Implantable Microstimulator and Systems Employing the Same); 6,175,764 (Implantable Microstimulator System for Producing Repeatable Patterns of Electrical Stimulation; 6,181,965 (Implantable Microstimulator System for Prevention of Disorders); 6,185,455 (Methods of Reducing the Incidence of Medical Complications Using Implantable Microstimulators); and 6,214,032 (System for Implanting a Microstimulator). The applications described in these additional patents, including the power charging techniques, may also be used with the present invention. The '596, '017, '764, '965, '455, and '032 patents are incorporated herein by reference.
Despite the various types of microstimulators known in the art, as illustrated by the examples cited above, significant improvements are still possible and desirable, particularly relative to positioning the microstimulator at a desired target site within the tissue to be stimulated.
Thus, it is seen that there is a need in the art for a simple electrode system that can be easily placed within soft tissue for the stimulation of nerves or muscles.